Cosmic microwave background radiation

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The cosmic microwave background (CMB) temperature fluctuations from the 7-year Wilkinson Microwave Anisotropy Probe data seen over the full sky. The image is a projection of the temperature variations over the celestial sphere.The average temperature is 2.725 Kelvin degrees above absolute zero (absolute zero is equivalent to -273.15 ºC or -459 ºF), and the colors represent the tiny temperature fluctuations, as in a weather map. Red regions are warmer and blue regions are colder by about 0.0002 degrees

Cosmic background microwave radiation (CMB radiation) is radiation in the microwave part of the electromagnetic spectrum, which comes from all directions in outer space. We know that it comes from very far away, so we think that it is the oldest signal that we can detect.

During the Big Bang, a lot of high-energy radiation was created. Then, the universe became bigger and colder. Therefore, the high-energy photons lost most of their original energy. Now, as a result, that radiation is in the microwave part of the electromagnetic spectrum (the microwave part has quite low energy). The cosmic microwave background is the radiation that has been travelling without hitting anything ever since the time the universe became transparent, about 380,000 years after the Big Bang.

Arno Penzias and Robert Wilson first detected the CMB radiation.[1] Scientists think that the existence of CMB radiation is important evidence, with red shift, that the Big Bang theory is true.

Later data is based on the Planck spacecraft operated by the European Space Agency (ESA). It was designed to observe differences in the cosmic microwave background (CMB) at microwave and infra-red frequencies, with high sensitivity and small angular resolution. The spacecraft has finished its work, but researchers are still analysing the data. The main interest is that there is:

"an asymmetry in the average temperatures on opposite hemispheres of the sky. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look. Furthermore, a cold spot extends over a patch of sky that is much larger than expected."[2] No explanation for this is known.

References[change | change source]

  1. Smoot Group 1996. The cosmic microwave background radiation. Lawrence Berkeley Lab. [1]
  2. Plank. European Space Agency 2013. [2]